Studies are continuing on a number of aspects of the phenomenology associated with the action of streptomycin and several other aminoglycoside antibiotics on E. coli. These studies are mainly directed at the mechanism by which these antibiotics interact with the ribosome and interrupt protein synthesis, with current efforts concerned with the development of photoactivatable derivatives of the antibiotics and their use in probing interactions with the ribosome. Efforts are also being devoted to obtaining a better understanding of the various phenotypes produced by mutations at the str locus, and by genetic suppression of these mutations. The question of ribosome turnover and biogenesis is also being explored as there appears to be a possible assembly defect in a majority of these mutants.